1. Field of the Invention
This invention relates generally to electronic identification and recognition systems and more specifically to such systems wherein it is not necessary to make physical contact between the identifier section and the reader section.
2. Description of the Prior Art
There are various electronic identification and recognition systems wherein the identifying device is portable. Sometimes the identifying device is referred to as a "card", "tag", "key", "identifier", "response unit", "transponder" or the like. The recognition station, also known as a interrogation unit or reader section, is prepared to recognize identifying devices of predetermined characteristics when such identifying device is brought within the proximity of the reader section.
Uses for such systems may include identification of persons having identifying devices in their possession. For example, the identifying device may take the shape of a credit card and have an electronic circuit embedded therein for radiating signals of identifying intelligence. An individual possessing the card may position it adjacent a door that the individual desires to enter. A recognition device may be arranged to control the door latch and if it recognizes radiated signals of a certain predetermined intelligence, the door latch responds to the reader when the individual places the card proximate to the reader. Other uses for such systems include having the identifier in the form of a tag attached to a vehicle to be identified. As the vehicle passes a certain location, such as a toll booth, its identification is recognized and recorded. Also, in production lines, garments or other items may carry identification tags so that they can be appropriately processed as they are recognized along various points in the production process.
The prior art includes various patents and patent applications by the present inventor The patents include U.S. Pat. No. 3,732,465 for "Electronic Sensing and Actuator System", issued May 8, 1973, U.S. Pat. No. 4,223,830 for "Identification System", issued Sep. 23, 1980; U.S. Pat. No. 4,236,068 for "Personal Identification and Signaling System", issued Nov. 25, 1980; U.S. Pat. No. 4,384,288 for "Portable Radio Frequency Emitting Identifier", issued May 17, 1983; U.S. Pat. No. 4,388,524 for "Electronic Identification and Recognition With Code Changeable Reactance", issued Jun. 14, 1983; U.S. Pat. No. 4,459,474 for "Identification System With Separation and Direction Capability and Improved Noise Reduction", issued Jul. 10, 1984; U.S. Pat. No. 4,473,825 for "Electronic Identification System With Power Input-Output Interlock and Increased Capabilities", issued Sep. 25, 1984; U.S. Pat. No. 4,546,241 for "Electronic Proximity Identification System", issued Oct. 8, 1985; U.S. Pat. No. 4,580,041 for "Electronic Proximity Identification System With Low Power Identifier, Simplified", issued Apr. 1, 1986; U.S. Pat. No. 4,600,829 for "Electronic Proximity Identification and Recognition System With Isolated Two-Way Coupling", issued Jul. 15, 1986; U.S. Pat. No. 4,654,658 for "Identification System With Vector Phase Angle Detection", issued Mar. 31, 1987; U.S. Pat. No. 4,656,472 for "Proximity Identification System With Power Aided Identifier", issued Apr. 7, 1987; and U.S. Pat. No. 4,782,342 for "Proximity Identification System With Lateral Flux Paths", issued Nov. 1, 1988. In addition, there is currently pending U.S. patent application Ser. No. 07/109,738, now abandoned, for "Electronic Proximity Vehicle Identification System With Dual and Single Frequencies", filed Oct. 19, 1987 and U.S. patent application Ser. No. 07/203,944, now U.S. Pat. No. 4,888,474 for "Proximity Identification System With Lateral Flux Magnetic Rod Coupling", filed Jun. 8, 1988.
The proximity identification systems of the prior art, which use inductive coupling, tend to have a limited range. The reader and identifier sections must be relatively close together for reliable data transmission between the two. There is a need for a proximity identification system with greater range and reliability of data transmission.